Modular implantable medical device and manufacturing method therefor

ABSTRACT

In an implantable medical device and a manufacturing method therefore, the implantable medical device has at least an electronics module and a battery module, each contributing functionally as well as to the shape of the outer enclosure of the implantable medical device. Different modules, and different versions of different modules, can be combined in different combinations, according to a device specification, to form different medical devices.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an implantable medical device and amanufacturing method therefore, of the type wherein the device isassembled from modules.

2. Description of the Prior Art

Several different ways to modularize and manufacture an implantablemedical device are known.

U.S. Pat. No. 5,370,669 describes an implantable defibrillator in whichthe components of the active implantable device are housed within animplantable casing having three orthogonal dimensions of height, widthand thickness. The height and width are substantially greater than theimplantable defibrillator comprises three major subsystems,specifically, the batteries, the power capacitors, and the electronics.The three sub-systems lie respectively in parallel height-width planes,each plane being adjacent another in the thickness dimension.

U.S. Pat. No. 5,103,818 describes an arrangement that enables rapid andeffective termination of electrical junctions for an implantable medicaldevice such as a heart pacemaker or an implantable defibrillator. Theelectronics subsystem and the battery are placed in one half of thehousing that also contains the feedthrough. At this moment the batteryand the feedthrough contact the electronics subsystem via femaleconnectors on the electronics subsystem. The electrical connections arethen fused welded. Following the fusion weld of the electricalconnections the other half of the housing is mounted and the enclosurewelded to become hermetic.

U.S. Pat. No. 5,814,091 describes an arrangement in which the battery isintegrated with the outer enclosure of the implantable medical device.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a modularized deviceallowing economically feasible manufacture of a large number of modelsof an implantable medical device and while limiting the number ofcomponents needed for the entire model program.

A further object is to simplify the process of assembling the finishedproduct.

A still further object is to shorten the development time for newproducts.

A still further object is to minimize the number of parts required forthe completed implantable medical device.

The above objects are achieved in accordance with the invention by animplantable medical device and a manufacturing method therefor whereinthe implantable device is divided into modules, each of the modulesforming a portion of the outer shape of the implantable medical device,and each of the modules performing (only) a well defined function of theimplantable device. A very important aspect is that one of the modulescan be modified without any need to modify any of the other modules. Themodules themselves have an open interface to other modules and as aconsequence the modules themselves are not hermetically sealed buthermetic sealing will be obtained when the modules are permanentlyattached to each other by e.g. laser welding. This will make it easy todevelop and manufacture different models of the implantable medicaldevice that have different connector modules or different batterymodules with a minimal cost for product development. If there are e.g.three different battery modules available, three different connectormodules and three different electronics modules available then 27different models of the finished products can be manufactured from thenine available modules. This will make it much easier for themanufacturer to adapt the production to varying market demands onbattery capacity or on connector type. It is also possible to upgradeproduction with a more advanced electronics module while connectormodule and battery module remain unchanged.

The present invention is particularly suitable for use in an implantablecardioverter defibrillator (ICD). In the ICD application therequirements regarding longevity and shock energy may vary significantlydepending on market requirements. One possible modularization for an ICDis to divide the ICD into four different modules according to theinvention. The individual modules may be as follows: module (a) couldessentially be a connector subsystem, module (b) could essentially be apower electronics subsystem including shock energy storage capacitors,power transformers etc, module (c) could essentially be low voltageelectronics such as pacing/sensing circuitry, module (d) couldessentially be a battery subsystem. By varying the size of module (b)with the power electronics subsystem the shock energy can be adapted todifferent needs through the use of shock energy capacitors of differentcapacitance. By varying the size of module (d) the battery subsystemcapacity the can be adapted to different requirements regardinglongevity and number of shocks available. It is also feasible to use ageneral set of modules suitable for pacemakers and for ICD's. In abradycardia pacemaker (a), (c) and (d) would be used while in an ICDmodules (a), (b), (c), and (d) would be used. The invention can also beutilized to add features to a standard pacemaker or ICD. As an example adiagnostic data collection module could be added to a standard pacemakeror ICD.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an implantable medical device inaccordance with the invention.

FIG. 2 shows how the manufacturing method can be implemented using threedifferent types for each of the three different modules necessary forthe production of an implantable medical device.

FIG. 3 is a sectional view of a first type of connector module for usein the implantable medical device of the invention.

FIG. 4 is a sectional view of a second type of connector module for usein the implantable medical device of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an example of an implantable cardiac pacemaker builtaccording to the invention. In this embodiment the cardiac pacemaker ismanufactured using three modules. Each of the modules contributesfunctionally as well as to the shape of the enclosure of the implantablemedical device. The following modules are used in this particularcardiac pacemaker: connector module 1 a,1 b,2,3 a,3 b,4, electronicsmodule 5 a, 5 b,6,7 and battery module 11.

The connector module 1 a,1 b,2,3 a,3 b,4 in this example is of the typein which the lead connectors are integrated into the housing without amolded plastic connector top. The connector module comprises thefollowing parts: metallic/ceramic connector tubes 1 a,1 b, a portion 2of the outer enclosure of the cardiac pacemaker, lead pin lockingwashers 3 a,3 b, a transparent plastic component 4, and flex circuits 5a,5 b. The metallic/ceramic connector tubes may for example be of thetype disclosed in international publication WO 00/12174. The flexcircuits 5 a,5 b provides electrical connection between themetallic/ceramic lead connecting tubes 1 a,1 b and the electronicsmodule 6. During manufacture the flex circuits 5 a,5 b are welded to afeedthrough portion of the connector tubes 1 a,1 b. The end portions ofthe connecting tubes 1 a,1 b are made of metal and are adapted to bewelded in both ends to the enclosure portion 2. Each of the flexcircuits 5 a,5 b is rolled on a connector tube and then the connectortube is inserted into the enclosure portion 2. After inserting the flexcircuit 5 a,5 b it is rolled out and the connector tube 1 a,1 b iswelded in both ends to the enclosure portion 2. The final step inassembling the connector module is to mount the locking washers 3 a,3 band the transparent plastic component 4. The purpose of the plasticcomponent 4 is to provide visible confirmation that the lead connectingpin is fully inserted into the implantable cardiac pacemaker at the timeof implantation. The finished connector module is a complete connectorfor the implanted lead, as well as a part of the outer shape of theenclosure of implantable device and it is adapted for a quick electricalconnection to an electronics module. During manufacture it is simplyconnected to the electronics module and then welded to the outerenclosure portion 7 of the electronics module. To facilitatemanufacturing the enclosure portion 2 of the connector module andenclosure portion 7 of the electronics module should be designed so thatthey have a very good fit to each other. Preferably outer enclosureportions such as 2 and 7 mentioned above should have a mechanical clickaction when they are properly oriented in relation to each other.

The electronics module 6,7 comprises an electronic circuit 6 and aportion of the enclosure 7. The electronics circuit 6 should preferablybe fixed to the enclosure portion 7 through gluing, or molding or othermethod. The electronic circuit 6 has a connection arrangement for aquick electrical connection of the connector top and the battery. Thisconnection arrangement should preferably be of a snap in type in orderto make welding, soldering or other more complicated connection methodsunnecessary, but these other connection methods nevertheless can be usedin the inventive device and method.

The battery module 11 serves as a power source as well as a portion ofthe outer enclosure. In a preferred embodiment the battery's enclosureis manufactured from titanium or any metal suitable for direct contactwith tissue. In that case the electrochemical potential of the batteryenclosure will become the enclosure potential of the implantable cardiacpacemaker. Thus one of the battery's electrical terminals is in directcontact with the patient's body tissue. This arrangement is particularlysuitable for Lithium/Carbon Monofluoride batteries that can bemanufactured with an enclosure of titanium. The outer enclosure of thebattery module 11 should preferably extend slightly above the lid of thebattery so that the outer encapsulation portion 7 of the electronicsmodule 5 a,5 b,6,7 can be welded directly to the enclosure of thebattery module 11 with no risk of jeopardizing the hermetic sealing ofthe battery during welding. In a more conventional embodiment anisolation layer is provided between the battery and the outer surface ofthe battery module to be able to more freely decide the electricalpotential of the finished implantable device's enclosure.

FIG. 2 is a schematic drawing indicating how an implantable medicaldevice can be built from different modules. The modules include aconventional connector top 21 and a connector module 22 of the typedescribed above that has no conventional molded connector top and aclosed connector top 23 without the feature of visual confirmation thatthe lead is properly inserted. The conventional connector top 21 has alower metallic portion with a connector top bottom and a flange to allowit to be welded to the electronic module 24, 25, 26. The metallicportion has conventional feedthroughs to allow an electric connectionbetween the electronic module 24, 25, 26 and the electrode leadconnectors in the connector top without compromising hermetic sealing.The connector top 21 alternatively can be manufactured in a ceramicmaterial. In the latter case there must be a metallic flange to allowwelding of the connector top to the remainder of the encapsulation.Feedthroughs are not necessary if the connector top is manufactured in aceramic material. Connection wires for connection between electrode leadconnectors and the electronic module will be located inside the ceramicmaterial in a fashion similar to a conventional feedthrough. 24, 25 and26 represent electronic modules of different size and shape. 27, 28 and29 represent battery modules of different size and capacity and alsopossible different electrochemical composition.

FIG. 3 shows the connector module 21 in a more detailed fashion. The topportion of the connector top is exactly similar to a conventionalconnector top. The metallic lower portion 31 has a bottom of theconnector top and a flange 36 used to weld the connector top 21 to anelectronics module 24, 25, 26. A feedthrough is welded to the lowermetallic portion. The top portion has a conventional molded portion 32,connector block with setscrew 33, a wire connection 34 for connectionbetween connector block 33 and feedthrough 30.

FIG. 4 shows a more detailed view of a connector module manufactured ofa ceramic material. The top portion of the connector top is manufacturedin a ceramic material Al₂O₃. Metal ribbons 39 a, 39 b provideselectrical connection between a heart electrode connector and theelectronics modules 24,25,26 with hermetic sealing of the enclosure forthe electronics being maintained. A metal rim 38 is soldered to thelower portion of the connector module. The connector module is welded tothe electronics module 24,25,26 by welding to the metal rim 38.

Every battery module 27,28,29 can be combined with every electronicsmodule 24,25,26 and every electronics module can be combined with everyconnector module 21,22,23. Thus 27 different models of the implantablemedical device can be produced using 9 different modules. This techniquewill make it easier to tailor the production to requirements from themarket. If, for example, one market requires a particular battery sizeor battery capacity the battery module can easily be replaced with asuitable module while no other changes have to be made. The connectormodules 21,22,23 can also be used for implantable medical devices havinga conventional encapsulation.

Although modifications and changes may be suggested by those skilled inthe art, it is the invention of the inventors to embody within thepatent warranted heron all changes and modifications as reasonably andproperly come within the scope of their contribution to the art.

1. An implantable medical device comprising: at least two functionalsubsystems each comprising at least one component and each formed as anon-hermetically sealed module having a module encapsulation thatcompletely covers said at least one component, at least one of saidsubsystems and the module thereof being available in multiple, differentversions; each module comprising an interface portion having aconfiguration allowing that module to mate with a correspondinginterface portion of any of the multiple versions of another of saidmodules, said modules being mechanically connected to each other at saidinterface portions when mated; the respective module encapsulations ofsaid modules, when mechanically connected to each other, formingrespective portions of an outer enclosure of a complete medical deviceformed by said modules; and mechanical connections that permanentlymechanically connect said respective module encapsulations with oneanother to hermetically seal said outer enclosure.
 2. A medical deviceas claimed in claim 1 wherein said plurality of modules comprise amodule comprising a battery subsystem, a module comprising an electronicsubsystem and a module comprising a connector subsystem.
 3. A medicaldevice as claimed in claim 1 wherein said plurality of modules includesa module comprising a battery subsystem, said module encapsulation ofsaid module comprising said battery subsystem being at a potential equalto a potential of said outer enclosure of said complete medical device.4. A medical device as claimed in claim 1 wherein said plurality ofmodules includes a module comprising a battery subsystem, said moduleencapsulation of said module comprising said battery subsystem being ata potential isolated from a potential of said outer enclosure of saidcomplete medical device.
 5. A medical device as claimed in claim 1wherein said plurality of modules include a module comprising a batterysubsystem utilizing a battery chemistry selected from the groupconsisting of lithium-iodine, lithium-silver vanadium oxide,lithium-carbon monofluoride, and a combination of lithium-silvervanadium oxide and lithium-carbon monofluoride.
 6. A medical device asclaimed in claim 1 wherein said plurality of modules includes a modulecomprising a battery subsystem, and wherein the module encapsulation ofthe module comprising said battery subsystem forms a portion of saidouter enclosure of said complete medical device.
 7. A medical device asclaimed in claim 1 wherein said plurality of modules includes a modulecomprising a connector subsystem, said module comprising said connectorsubsystem being selected from the group consisting of a modulecomprising a connector subsystem with one pacing/sensing terminal, amodule comprising a connector subsystem with two pacing/sensingterminals, a module comprising a connector subsystem with threepacing/sensing terminals, and a module comprising a connector subsystemwith four pacing/sensing terminals.
 8. A medical device as claimed inclaim 1 wherein said plurality of modules includes a module comprising aelectronics subsystem, said module comprising said electronics subsystembeing selected from the group consisting of a module comprising aelectronics subsystem with one pacing/sensing terminal, a modulecomprising a electronics subsystem with two pacing/sensing terminals, amodule comprising a electronics subsystem with three pacing/sensingterminals, and a module comprising a electronics subsystem with fourpacing/sensing terminals.
 9. A medical device as claimed in claim 1wherein said mechanical connections are laser welds.